1. Field of the Invention
The invention relates to a clamping jaw for a clamping chuck of a tool holder for paired use with an oppositely positioned clamping jaw, wherein the clamping jaw and the oppositely positioned clamping jaw are positioned diametrically opposite and spaced apart to one another relative to the axis of rotation of the clamping chuck and, by moving the clamping chuck with a radial component, can be moved toward one another and away from one another for clamping or releasing a tool shaft, wherein each clamping jaw comprises a longitudinal slot open toward the axis of rotation of the clamping chuck for positive-lockingly receiving the tool shaft.
2. Description of the Related Art
Clamping jaws with these features are known, for example, from a brochure published by Robert Schrxc3x6der GmbH and Co. KG, Germany.
Such clamping jaws comprise longitudinal slots which extend substantially axially to the axis of rotation of the clamping chuck and are provided for receiving in a positive-locking way a tool shaft.
Such tool shafts are provided, for example, as square shafts on screw taps or as hexagonal shafts on so-called drill bits.
The term tool holder in the context of the present invention is meant to include also so-called wrenches of screw taps which are generally configured to receive the usually square tool shaft of the screw tap.
In any case, an important feature of such clamping jaws, however, is the preparation for a positive-locking engagement of the tool shaft in order to be able to introduce via the tool holder great torque into the tool, respectively, without there being the risk of slipping of the tool.
Polygonal drive shafts of such tools are then secured positive-lockingly between the clamping jaws of the tool holder which are arranged in pairs, respectively, and cannot slip within the clamping chuck even at highest torques since they do not have radial symmetry.
It is an object of the present invention to improve the known clamping jaws such that they are suitable for receiving polygonal tool shafts of different cross-sections.
In accordance with the present invention, this is achieved in that the approach angle of the longitudinal slot is greater than the slot bottom angle.
The invention has the advantage that with one and the same tool holder the diametrically oppositely positioned edges or corners of a square tool shaft as well as of a hexagonal tool shaft can be received in a positive-locking way without the clamping jaw pair having to be exchanged prior to clamping, respectively.
For this purpose, the longitudinal slot has two slot flank angles of different size wherein the larger slot flank angle determines the approach cross-section at the mouth of the longitudinal slot while the smaller one defines the slot bottom angle.
The slot flanks of the longitudinal slot, which receive two neighboring polygon sides between them, thus can receive, as a function of the polygon cross-section of the tool shaft, on the one hand a tool shaft having a larger angle and on the other hand a tool shaft having an angle corresponding to the smaller slot bottom angle. In both cases, the longitudinal slot is configured for a positive-locking engagement of a tool shaft wherein two neighboring polygon sides define a predetermined slot flank angle between them.
Without limiting the invention to tool shafts with hexagon and square cross-sections, most application requirements of clamping jaws will be solved with the larger approach angle of the longitudinal slot being 120xc2x0 and the smaller slot bottom angle being 90xc2x0.
According to this embodiment of the invention, the approach angle of 120xc2x0 is provided for a positive-locking engagement of a hexagon cross-section while the slot bottom angle is provided for a positive-locking engagement of a square cross-section.
It is important in connection with the invention that, because of the paired use of the clamping jaws, the tool shaft is provided with a cross-section of a regular polygon with an even number of polygon sides. This requirement ensures that, with respect to the axis of rotation of the tool holder, two polygon corners are positioned diametrically opposite one another, respectively, which are inserted into the corresponding longitudinal slot of the clamping jaws and are then clamped radially by a movement of the longitudinal slots toward one another.
The longitudinal slots can have an edge at the transition from the approach angle to the slot bottom angle. However, the longitudinal slot can also be rounded at this transitional location so that the contour of the rounded arc or curve extends or tapers tangentially into the slot flanks defining the approach angle as well as into the slot flanks which define the slot bottom angle.
According to another embodiment, the longitudinal slot can also have convexly curved slot flanks with at least two tangents in the area of the approach angle and of the slot bottom angle which fulfill the aforementioned condition.
In this way, it is ensured that, even under consideration of tool wear, the condition as defined above, i.e., the approach angle being greater than the slot bottom angle, is always fulfilled during the manufacture of these clamping jaws.
Advantageously, the present invention is based on the feature that the tool shaft exclusively has surface lines which extend parallel to one another so that all the surface lines of the longitudinal slot extend parallel to the axis of rotation.
In this way, the tool shaft can be reliably clamped in the axial direction without additional clamping components.
In this connection, the expenditure for the invention, in comparison to the achieved advancement, is minimal.
In deviation from the prior art, it is only necessary to employ a disc milling cutter for manufacturing such clamping jaws, wherein the oppositely positioned milling cutter flanks are positioned at a slant to one another first at a small angle and then at a greater angle in the radial direction from the exterior to the interior.
With such a tool, a clamping jaw according to the invention can be produced in a single working step without this requiring any tool change, as used to be the case in the sequential manufacture of a first slot flank angle and then a second slot flank angle.
When, furthermore, a certain wear on such a disc milling cutter for producing such clamping jaws is taken into consideration, further embodiments are conceivable which are produced by means of an already worn disc milling cutter, i.e., the smallest slot flank angle being smaller or identical to 90xc2x0 and the greatest slot flank angle being greater or identical to 120xc2x0; or only two slot flank angles are provided, wherein the smaller one is 90xc2x0 and the greater one is 120xc2x0.
These measures increase thus the possible service life of such manufacturing tools without deviating from the basic principle of the invention.